Adversaries may use bootkits to persist on systems. A bootkit is a malware variant that modifies the boot sectors of a hard drive, allowing malicious code to execute before a computer's operating system has loaded. Bootkits reside at a layer below the operating system and may make it difficult to perform full remediation unless an organization suspects one was used and can act accordingly. In BIOS systems, a bootkit may modify the Master Boot Record (MBR) and/or Volume Boot Record (VBR).(Citation: Mandiant M Trends 2016) The MBR is the section of disk that is first loaded after completing hardware initialization by the BIOS. It is the location of the boot loader. An adversary who has raw access to the boot drive may overwrite this area, diverting execution during startup from the normal boot loader to adversary code.(Citation: Lau 2011) The MBR passes control of the boot process to the VBR. Similar to the case of MBR, an adversary who has raw access to the boot drive may overwrite the VBR to divert execution during startup to adversary code. In UEFI (Unified Extensible Firmware Interface) systems, a bootkit may instead create or modify files in the EFI system partition (ESP). The ESP is a partition on data storage used by devices containing UEFI that allows the system to boot the OS and other utilities used by the system. An adversary can use the newly created or patched files in the ESP to run malicious kernel code.(Citation: Microsoft Security)(Citation: welivesecurity)

Linked Issues

Issuelinks
Linktyp Issue
is related to Techniques
is blocked by Detection Strategy for File Creation or Modification of Boot Files
is blocked by Boot Integrity
is blocked by Privileged Account Management
is blocked by Asset Inventories
is blocked by Configuration Change Control
is blocked by Access Restriction For Change
is blocked by Secure Baseline Configurations
is blocked by Endpoint File Integrity Monitoring (FIM)
is blocked by Separation of Duties (SoD)
is blocked by Identification & Authentication for Organizational Users
is blocked by Identification & Authentication for Non-Organizational Users
is blocked by Cryptographic Module Authentication
is blocked by Account Management
is blocked by Access Enforcement
is blocked by Least Privilege
is blocked by Non-Modifiable Executable Programs
is blocked by Criticality Analysis During Development
is blocked by Security, Compliance & Resilience Testing Throughout Development
is blocked by Developer Configuration Management
is blocked by Software & Firmware Patching
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